Three of the candidates - Jeb Bush, Scott Walker and Marco Rubio - were asked to "band together" and "refuse to debate" - if Trump was on stage, according to the report. But they rejected the plea, worried that it would make him a "martyr".

On Wednesday night, Trump gave yet another impassioned interview as he spoke to CNN's Anderson Cooper - but he wasn't happy when the host mentioned a new poll showing Trump with an "unfavorable" rating.

"You only want to talk about negative," Trump said. "Why don't you bring up the positive polls, Anderson?